This invention relates generally to devices for monitoring stress and strain in dynamic structures and more particularly to transducers for measuring the output torque of power tools and other rotating machinery.
Monitoring of dynamic stresses and strains in power tools and other rotating machinery is often desirable. The data received from such operations permit evaluation of the performance of the equipment in question. In the case of power tools, such as nutrunners or screwdrivers, the data permit measurement of the torque output and thereby calculation of fastener tension produced by the tool. Real time feedback coupled with programmable controls makes it possible to automatically deactivate the tool power when a desired fastener tension is achieved. This provides the benefit of reproducible fastener tensioning in assembly line or other mass production operations. A variety of transducers are available for measuring torque output of rotating machines. In many cases, the axial dimensions of the transducer are such that their use requires an unacceptable increase in the size of the tool. When the tool must be used in a limited space environment, such size increases may be intolerable. In such cases, fastener tension can only be determined by use of tortuous tool combinations of questionable accuracy. In addition, an excessive increase in size can contribute to increased weight and unwieldy proportions which can contribute to premature operator fatigue and otherwise degrade operator performance.